The present invention relates to rechargeable batteries for mobile telephones, and relates more particularly to an assembly which combines a rechargeable battery with a charging circuit for converting AC supply power to DC supply power to charge the battery.
The battery of a mobile telephone must be regularly charged so that sufficient battery power supply can be constantly maintained to insure proper operation of the mobile telephone. Mobile telephones typically draw 60-70 mA of current during standby operation and 600-700 mA of current during calling operation. Therefore, with a mobile telephone battery having a capacity of about 600-700 mAH, a typical mobile telephone can operate for about 10 hours in standby mode or for approximately one hour in the calling mode. In order to charge the battery frequently, a mobile telephone user must carry a battery charger. However, when a mobile telephone battery is frequently charged, a battery memory effect tends to occur, causing the effective capacity of the battery to diminish. If this battery memory effect is not negated, the battery cannot be fully charged to the rated capacity. This battery memory effect greatly shortens the service life of the battery. In addition, when the battery is charged to saturation by a battery charger, the battery charger does not cut off the power automatically; therefore, the battery may be overcharged and thereby damaged. Conventional battery chargers are commonly comprised of a transformer and rectifier circuit for converting AC supply power to DC supply power. The use of a transformer, however, greatly increases the weight and size of the battery charger.